Application of waste tyre-based activated carbon for the removal of heavy metals in wastewater

Figures & data

Table 1. Factors and level used in the factorial design

Variables	Minimum	Central point	Maximum
pH	4	6.5	9
Concentration of solution (mol L^−1)	10	55	100
Contact time (min)	5	32.5	60
Mass of adsorbent	0.1	0.2	0.3

Table 2. Selection of the suitable activating agent

Code name	Acid (mL)	Ratio (adsorbent:acid)
WT-AC-1	H3PO4	1:5
WT-AC-2	H3PO4	1:10
WT-AC-3	H2O2	1:5
WT-AC-4	H2O2	1:10

Notes: WT-AC: waste tyre activated carbon, Temperature: 200°C; time: 120 min; carbon powder: 0.3 g.

Table 3. Surface and pore structure of the developed tyre-based activated carbon

Sample name	SBET (m^2 g^−1)	Ssinglepoint(m^2 g^−1)	Vmicro(cm^3 g^−1)	Vmeso(cm^3 g^−1)	VTotal(cm^3 g^−1)
Raw-Carbon	8.052	7.781	0.001	0.108	0.109
WT-AC-1 (1:5)	33.567	32.113	0.041	0.293	0.334
WT-AC-2 (1:10)	45.572	44.684	0.011	0.332	0.343
WT-AC-3 (1:5)	39.128	37.680	0.032	0.438	0.470
WT-AC-4 (1:10)	48.792	47.805	0.047	0.987	1.034

Notes: WT-AC: Waste tyre activated carbon; S_BET: Surface area of BET; S_singlepoint: Surface area of a single point; V_micro: Volume of microporosity; V_meso: Volume of mesoporosity; V_Total: Total volume.

Figure 1. SEM micrograph of the (a) raw carbon black and (b) produced activated carbon (WT-AC-4).

Table 4. The design matrix and the results of the two-level (2⁴⁻¹) fractional factorial design

Runs	pH	Concentration (ppm)	Mass of adsorbed (g)	Contact time (min)	Removal (%)
					Cd	Pb
1	4	10	0.1	5	81	76
2	4	100	0.1	60	79	71
3	4	10	0.3	60	82	67
4	4	100	0.3	5	71	75
5	9	10	0.1	60	23	34
6	9	100	0.1	5	26	28
7	9	10	0.3	5	33	40
8	9	100	0.3	60	25	32
9	6.5	55	0.2	32.5	87	89
10	6.5	55	0.2	32.5	89	90
11	6.5	55	0.2	32.5	86	87

Figure 2. Pareto chart for Cd and; (b) Pareto chart for Pb (IC: Initial concentration; MA: Mass of adsorbent; CT: Contact time).

Table 5. Validation and application of the optimized tyre-based activated carbon in domestic wastewater and surface water

Analytes	%R-SRM	%RSD	%R-IW	%R-EW	%R-SS1	%R-SS2	%R-SS3
Cd	99	3.9	77	74	94	96	93
Pb	98	3.7	83	87	90	92	91

Notes: Percentage removal efficiency (%R); relative standard deviation (%RSD); influent wastewater (IW); effluent wastewater (EW); surface water sample (SS).